Cross-platform split + publish tokens + extract hooks

[bntvllnt]

• Split into /core (headless) · /web (React DOM) · /native (Expo/React Native)
• Publish design /tokens as platform-neutral JSON → feeds web CSS vars + native StyleSheet (single source)
• DRY the tailwind preset (currently duplicated across configs)
• Extract the zero-dep hooks (useDebounce, useMounted, useMediaQuery, …) into a standalone shared hooks entry point; keep design-bound hooks here

[github-actions]

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